Apparatus for reproducing recorded data

ABSTRACT

In an apparatus for reproducing recorded data, a crosstalk signal is generated by converting adjacent data recorded on an adjacent track into a waveform of said reproduction signal and the crostalk signal is deducted from the reproduction signal. Then, the reproduction signal in which the crosstalk signal is eliminated is decoded in accordance with the predetermined algorithm and reproduced.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to an apparatus forreproducing recorded data and a record format to record data, and moreparticularly to the apparatus for reproducing recorded data thatreproduces a target track to be reproduced and an adjacent track by onebeam, a crosstalk signal is generated, and the crosstalk is cancelled bydeducting the crosstalk signal from a reproduction signal.

[0003] 2. Description of the Related Art

[0004] To record data, various recording media have been provided suchas a magnetic disk, a magnetic tape, an optical disc, and amagneto-optical disc. In order to record data on these recording media,a magnetic record mark is mainly used, since compared with semiconductormemory, data can be permanently stored at a low cost. Thus, apparatususing these recording media have been essentially needed to recordinformation such as a graphic, image information or a like, forcomputers, at a present age in which much information is dealt with.

[0005]FIG. 1 is a diagram showing an example of a circuit configurationof a conventional data reproducing apparatus.

[0006] An optical head 11 reproduces a signal from a recording medium 10such as an optical disk or a magneto-optical disc. In order to recognizean address at which information is recorded, an SUM/ID detector 19detects address information from a SUM signal or a Wobble signal, andthen an ODC (optical control circuit) 20 recognizes the address.

[0007] Moreover, a reference clock CLK is made from a PLL (Phase-LockedLoop) 18 synchronizing with a signal from a clock mark provided on therecording medium 10 for reproducing data. A signal process is conductedbased on this reference clock CLK and then data is detected.

[0008] A reproduction signal from the optical head 11 is amplified by anamplifier 12, a high frequency noise is eliminated by a LPF (low passfilter) 13, and then the reproduction signal is supplied to an ADC (A/Dconverter) 14. A high-pass filter is not shown in FIG. 1 but isgenerally provided for low-pass fluctuation suppression and circuitsaturation prevention. Alternatively, an analog equalizer may be usedfor waveform equalization.

[0009] The ADC 14 samples by a reference clock CLK supplied from the PLL18. In a case in which data recording condition is different for each ofdata reproducing apparatuses, a phase of the reproduction signal may beshifted from that of the clock synchronized with the clock mark formedby the pre-pit. For this reason, the phase of the reference clock CLK(not shown in FIG. 1) may be adjusted.

[0010] An EQ (digital equalizer) 15 equalizes and forms a waveform basedon a sample value sampled by the ADC 14. Then, the sample value isequalized into a PR (Partial Response) signal. The PR signal is detectedby a ML (most-likelihood) detector 16 and then is decoded by a decoder17.

[0011] Decoded data is sent to the ODC 20, and an ECC decode is carriedout. An ECC (Error Correcting Code) check is conducted for the decodeddata. FIG. 2 is a schematic diagram showing an example of a format. InFIG. 2, a simplified 2K ECC Block disk format of AS-MO (AdvancedStorage-Magneto Optical Disk) Physical Specifications (Version1.0 April1998) is shown.

[0012] Referring to FIG. 2, a header 21 is provided before data part 29and either one of 2T-repeated data in which a bit string “1100” isformed, and 8T-repeated data in which a bit string “1111111100000000” isformed, is recorded. For example, an Auto Read Power Control Area 22 isto be used in order to measure amplitude of the 2T-repeated data and theamplitude of the 8T-repeated data and to adjust reproduction power. AnAuto Gain Control Area 23 is used to adjust the amplification gain of asignal. A Read Clock Phase Control Area 24 is used to adjust the phaseof the reference clock CLK made by PLL synchronization with the clockmark mentioned above, with the phase of the clock for sampling a datasignal. A Buffer Area 25 is provided before the data part 29.

[0013] In such general formats including ISO specification or a like, asimilar signal is also recorded on an adjoining track. Of course in thedata part 29, unknown random data is recorded on the adjacent track.

[0014] However, there are problems described as follows in theconventional data reproducing method.

[0015] In order to improve an optical disk in high density, bit densityand track density may be enlarged. As to improve in high density ofbits, a technology such as a PRML (Partial Response Maximum Likelihood)technology using waveform interference is well known. However, if thetrack density is made high, cross-write and crosstalk occur.

[0016] The cross-write is a phenomenon in which when data is recorded ona track to be recorded by higher power than optimal power, the data isalso recorded on an adjacent track of the track. The cross-write deletesinformation currently recorded on the adjacent track. Thus, aninformation signal quality of the adjacent track is deteriorated. A heatdistribution on an optical disk is controlled by properly conductingstrobe luminescence and power adjustment of a LD (Laser Diode), so as toavoid the cross-write. Crosstalk is a phenomenon in which the adjacenttrack signal intermixes in a beam spot when data is reproduced and ajitter is caused in the signal to be reproduced. Especially if the trackdensity becomes higher, the crosstalk cannot be avoided.

[0017] The conventional technology (Japanese Laid-Open PatentApplication No.58-121138, Japanese Laid-Open Patent ApplicationNo.5-205280) is known in which data recorded on the adjacent track isdetected, the crosstalk signal is generated from the data, a crosstalkamount is measured, and then the crosstalk is canceled by deducting thecrosstalk signal generated from a reproduction signal. In thisconventional technology, the adjacent track signal is alsosimultaneously reproduced by three beams, and the crosstalk is canceledby adjusting and deducting gain. However, since three beams are neededin order to carry out simultaneous reproduction of the adjacent tracksignal in this conventional technology, it is difficult to adjust phasedifferences by distance differences among the three beams.

[0018] Moreover, in the conventional technology (Laid-Open PatentApplication No.5-205280), a reproduction waveform by scanning two tracksincluding an adjacent track by one beam is sampled by an ADC (Analog toDigital Converter), and a sample value is stored in a storage area,beforehand. The sample value is used and the crosstalk is cancelled whendata recorded on a target track is reproduced. However, the ADC, whichconverts one sample value into 6 bit (through 8 bit) data, is used. Thehuge storing area, that is, 6 bit (through 8 bit)×sample number(waveform length in which the crosstalk is cancelled)×two tracks, isneeded as a storage area.

[0019] Furthermore, it is known that the pre-pit signal and the Wobblesignal in an area to which address information is stored depend on adiameter of the beam spot. If track density is raised, the pre-pitsignal or the Wobble signal is influenced by the adjacent track signalbefore an MO signal that read data information (such as user data)Consequently, crosstalk data cannot be reproduced. For this reason, in aconventional technology (Laid-Open Patent Application No.8-231139), amethod of suppressing interference is proposed in that an adjacentpre-pit signal is shifted in a direction of arranging bits. However, insuch a configuration, since an additional area is needed in thedirection of arranging bits, a format effect becomes degraded. Even insuch the configuration, when the track density is raised further, thecrosstalk occurs. That is, in a case in which the track density israised further, when the beam spot overflows a track, a signal forreproduction is superimposed with an adjacent track signal by thecrosstalk. Then, the signal superimposed causes a jitter and areproduction signal quality is degraded. Accordingly, an error rate ofdata is increased and the data cannot be reproduced correctly.

SUMMARY OF THE INVENTION

[0020] It is a general object of the present invention to provide anapparatus for reproducing recorded data in which the above-mentionedproblems are eliminated.

[0021] A more specific object of the present invention is to provide theapparatus for reproducing recorded data that generates a crosstalksignal by reproducing an adjacent track while simultaneously reading atarget track and at least one adjacent track by one beam, and cancelsthe crosstalk by deducting the crosstalk signal from the reproductionsignal.

[0022] The above object of the present invention is achieved by anapparatus for reproducing recorded data by decoding a reproductionsignal read from the recorded data recorded on a recording medium inaccordance with a predetermined algorithm, the apparatus including: acrosstalk signal generating part generating a crosstalk signal byconverting adjacent data recorded on an adjacent track into a waveformof the reproduction signal; and a crosstalk signal eliminating parteliminating the crostalk signal by deducting from the reproductionsignal, wherein the reproduction signal in which the crosstalk signal iseliminated is decoded in accordance with the predetermined algorithm andreproduced.

[0023] In the apparatus for reproducing recorded data, it is possible togenerate the crosstalk signal from the adjacent rack and eliminate thecorsstalk signal, which is generated, from the reproduction signal fromthe target track to be reproduced.

[0024] Accordingly, it is possible to improve the quality of thereproduction signal from recorded data that is recorded on the recordingmedium where tracks are arranged at high density.

[0025] From a viewpoint of eliminating the crosstalk when datainformation (user data) is reproduced, the apparatus may further includea storing part having at least one memory and storing detected datadetected by the predetermined algorithm when the recorded data is userdata, wherein the crosstalk signal generating part generates thecrosstalk signal by converting the detected data stored in the storingpart into the waveform of the reproduction signal, and the reproductionsignal showing the user data, in which the crosstalk signal iseliminated by the crosstalk signal eliminating part, is decoded by thepredetermined algorithm and reproduced.

[0026] In the apparatus according to the present invention, since thedetected data detected in accordance with the predetermined algorithm isstored and also the detected data is a bit value, it can be realized toeliminate the crosstalk by less storage area.

[0027] Conventionally, 6 bit (through 8 bit) sample data is stored.According to the present invention, only one bit is required to store.It is possible to realize by less storage area (⅛ through ⅙ storagearea) than the conventional method. Moreover, since the crosstalk fromthe adjacent track only is considered by the off-track, it is possibleto reduce the storage area to half area. Consequently, it is possible toreduce the storage amount greater than the conventional method({fraction (1/16)} through {fraction (1/12)} the storage amount of theconventional method).

[0028] From a viewpoint of obtaining a precise crosstalk amount, theapparatus may further include a measurement data recording partrecording a predetermined measurement data to measure a crosstalkamount; and an elimination ratio obtaining part obtaining the crosstalkamount based on the measurement data read from the recording medium andobtaining a crosstalk elimination ratio, wherein the crosstalk signalgenerated by the crosstalk signal generating part is eliminated from thereproduction signal based on the crosstalk elimination ratio.

[0029] In the apparatus according to the present invention, it ispossible to obtain the precise crosstalk amount by reading thepredetermined measurement data recorded on the recording medium. Also,it is possible to variably eliminate the crosstalk signal from thereproduction signal by the crosstalk elimination ratio.

[0030] From a viewpoint of realizing a media compatibility, theapparatus may further include a zero data storing part storing zero dataonly wherein the crosstalk signal generating part obtains the zero datafrom the zero data storing part when the crosstalk signal is notgenerated.

[0031] In the apparatus according to the present invention, thecrosstalk signal is generated base on the zero data. As a result, thecrosstalk signal is not generated. Therefore, it is possible to realizethe media compatibility for a recording medium where data is recorded byanother recording apparatus.

[0032] From a viewpoint of generating the crosstalk signal from thereproduction data, the apparatus may further include a read signalconverting part converting decoded data into a read signal for readingthe recorded data recorded on the recording medium, wherein the storingpart stores the decoded data, the read signal converting part convertsthe decoded data stored by the storing part into the read signal, andthe crosstalk signal generating part converts the read signal convertedby the read signal converting part into the waveform of the reproductionsignal.

[0033] In the apparatus according to the present invention, data decodedand output as reproduction data can be converted into the reproductionsignal. Therefore, even in a case of using a code, such as a run lengthlimited code, having a longer length after encoded than before encoded,it is possible to eliminate the crosstalk signal from the reproductionsignal.

[0034] From a viewpoint of generating the crosstalk signal from data inwhich an error is corrected, the apparatus may further includes a readsignal converting part converting corrected data into the read signalfor reading the recorded data recorded on the recording medium, whereinthe storing part converts the corrected data stored by the storing partinto the read signal and the crosstalk signal generating part convertsthe read signal converted by the read signal converting part into thewaveform of the regeneration signal.

[0035] In the apparatus, since the crosstalk signal is generated fromdata in which error is corrected, it is possible to eliminate a moreprecise crosstalk signal from the reproduction signal.

[0036] From a viewpoint of eliminating the crosstalk by reading twotracks, the apparatus may further includes a read controlling partcontrolling to read the recorded data recorded on a target track to bereproduced by an off-track, wherein the crosstalk signal eliminatingpart eliminates an actual crosstalk signal caused by the off-track fromone side of an adjacent track, by deducting the crosstalk signalgenerated by the crosstalk signal generating part from the reproductionsignal.

[0037] In the apparatus, since two track are simultaneously read by theoff-track, it is possible to improve an accuracy of the reproductionsignal by simply eliminating the crosstalk signal occurred from theadjacent track only.

[0038] From a viewpoint of eliminating the crosstalk by reading threetracks, the apparatus may further includes a target reproduction signalstoring part storing the reproduction signal read from a target track tobe reproduced, wherein: the storing part includes two memories andstores a previous detected data detected from a previous track of thetarget track and a next detected data detected from a next track of thetarget track; the crosstalk signal generating part generates a previouscrosstalk signal and a next crosstalk signal based on the previousdetected data and the next detected data; and the crosstalk signaleliminating part deducts the previous crosstalk signal and the nextcrosstalk signal from the reproduction signal stored in the targetreproduction signal storing part.

[0039] In the apparatus, two crosstalk signals are generated from twoadjacent tracks by reading three tracks. Therefore, it is possible toimprove an accuracy of the reproduction signal more by eliminate the twocrosstalk signals from the reproduction signal.

[0040] From a viewpoint of eliminating the crosstalk when the addressinformation is reproduced, when the recorded data is addressinformation, the crosstalk signal generating part generates thecrosstalk signal by converting adjacent address information adjacent tothe recorded data into the waveform of the reproduction signal, so thatthe reproduction signal showing the address information, in which thecrosstalk signal is eliminated by the crosstalk signal eliminating part,is decoded in accordance with the predetermined algorithm to reproduce.

[0041] In the apparatus, it is not required to read the adjacent addressinformation. It is possible to generate the crosstalk signal byconverting into the waveform of the reproduction signal.

[0042] Therefore, without degrading the format effect in the addressinformation area, it is possible to cancel the crosstalk of the addresssignal. Moreover, higher track density can be realized. Thus, it ispossible to improve the recording density by an improved format effect.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other objects, features and advantages of the present inventionwill become more apparent from the following detailed description whenread in conjunction with the accompanying drawings, in which:

[0044]FIG. 1 is a diagram showing an example of a circuit configurationof a conventional data reproducing apparatus;

[0045]FIG. 2 is a schematic diagram showing an example of a format;

[0046]FIG. 4A and FIG. 4B are diagrams showing the state of thereproduction signal;

[0047]FIG. 5 is a diagram showing an example of the second format;

[0048]FIG. 6 is a diagram showing a configuration example of a firstreproduction circuit;

[0049]FIG. 7 is a diagram showing a sampling example of the PR(1,1)waveform;

[0050]FIG. 8 is a diagram showing an example of the circuitconfiguration of the peak bottom detector;

[0051]FIGS. 9A, 9B, 9C and 9D are diagrams showing a sequence example ofa crosstalk cancel gain when the track jump is conducted;

[0052]FIG. 10 is a diagram showing a relationship between a successivetrack reproduction number and the crosstalk cancel gain;

[0053]FIG. 11 is a diagram showing an optical hard disk format;

[0054]FIG. 12 is a diagram showing a configuration example of the secondreproduction circuit;

[0055]FIG. 13 is a diagram showing a memory configuration example insidethe single memory for each sector;

[0056]FIG. 14 is a diagram showing a configuration example of the thirdreproduction circuit;

[0057]FIG. 15 is a diagram showing a configuration example of the fourthreproduction circuit;

[0058]FIG. 16 is a diagram showing an example of the third format;

[0059]FIG. 17 is a diagram showing a configuration example of the fifthreproduction circuit;

[0060]FIG. 18 is a diagram showing an effect of the crosstalkcancellation;

[0061]FIG. 19 is a diagram showing a spot position of the optical beamwhen the address part is reproduced;

[0062]FIG. 20 is a diagram showing a configuration example of a sixthreproduction circuit;

[0063]FIG. 21A is a diagram showing a record example of the pre-pit,

[0064]FIG. 21B is a diagram showing the reproduction signal of the trackT2n−1 only,

[0065]FIG. 21C is a diagram showing the reproduction signal of the trackT2n only, and

[0066]FIG. 21D is a diagram showing a synthesized reproduction signal ofthe track T2n−1 and the track T2n;

[0067]FIG. 22 is a diagram showing an example of waveform change causedby a crosstalk amount and a phase shift;

[0068]FIG. 23 is a diagram showing a relationship between the amplituderatio and the crosstalk amount; and

[0069]FIG. 24 is a diagram showing a circuit configuration example ofthe crosstalk gain calculator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0070] An embodiment according to the present invention will now bedescribed with reference to figures.

[0071] In a data reproducing apparatus according to the embodiment ofthe present invention, for example, data is recorded on a recordingmedium in accordance with a first format as shown in FIG. 3.

[0072]FIG. 3 is a diagram showing an example of the first format.

[0073] In FIG. 3, a predetermined signal, for example, an area 41recording 2T-repeated data is arranged so as to shift every track fortwo tracks in a measurement area of crosstalk. A blank area 42 is anarea where no data is recorded. Moreover, a data part 29 is shown suchas Data 2n−1, Data 2n, and Data 2(n+1)−1 every track.

[0074] In the first format shown in FIG. 3, an optical beamsimultaneously irradiates two tracks T2n−1 and T2n such as a spot 40.Like the spot 40, a state of a reproduction signal reproducing recordeddata (data such as user data recorded on a recording medium 10) byemitting an optical beam (not shown) is shown in FIG. 4A and FIG. 4B.

[0075]FIG. 4A and FIG. 4B are diagrams showing the state of thereproduction signal.

[0076] In FIG. 4A, if an ideal reproduction is conducted so that nocrosstalk occurs at tracks T2n−1 and T2n of the first format, thereproduction signal occurs in the area 41 of the 2T-repeated data andthe data part 29 at each of the tracks T2n−1 and T2n but does not occurother than in the tracks T2n−1 and T2n.

[0077] However, for example, in a case in which the track T2n isreproduced, since the crosstalk occurs by the reproduction signal fromthe adjacent track T2n−1, the reproduction signal from the track T2nincludes the crosstalk as shown in FIG. 4B.

[0078] In FIG. 4B, if the track T2n is to be reproduced and a signalamplitude V_(A) is of the track T2n, the crosstalk signal from theadjacent track T2n−1 is reproduced such as a signal XT_(A) and thecrosstalk signal has the signal amplitude V_(A) depending on a crosstalkamount.

[0079] In the present invention, as shown in FIG. 4B, gate signals GateA and Gate B are created, the crosstalk amount of each of the gatesignals Gate A and Gate B is measured, and signal amplitudes V_(A) andV_(B) are measured.

[0080] In a case in which the example of the conventional format shownin FIG. 2 is applied to the first format shown in FIG. 3, in accordancewith which first format the data reproducing apparatus records data,according to the embodiment of the present invention, for example, aconventional existing area can be configured as a measurement area suchas a second format shown in FIG. 5.

[0081]FIG. 5 is a diagram showing an example of the second format.

[0082] Referring to FIG. 5, by changing the position and capacity of anarea (Buffer Area) 25, a Read Clock Phase Control Area 24 is arranged soas to shift for every track. By forming a stagger, areas for obtainingcrosstalk gain are provided. In the example of the second format of FIG.5, the Read Clock Phase Control Area 24 is used as a measurement area ofthe crosstalk.

[0083] With reference to FIG. 6, a reproduction circuit will now bedescribed in that the crosstalk is cancelled while reproducing datarecorded in accordance with the first format or the second format wherethe stagger is formed.

[0084]FIG. 6 is a diagram showing a configuration example of a firstreproduction circuit. In FIG. 6, a portion 150 surrounded by a dottedline shows a characteristic configuration in the first reproductioncircuit. In FIG. 6, the first reproduction circuit includes an opticalhead 11 for reading recorded data from the recording medium 10, anamplifier 12 for amplifying a reproduction signal, a LPF (low passfilter) 13 for eliminating a high frequency noise, an ADC (A/Dconverter) 14 for converting the reproduction signal into digital data,a EQ (digital equalizer) 15 for equalizing to a predetermined waveform,a calculator 55 for deducting the crosstalk from the reproductionsignal, a ML (most-likelihood) detector 16 for detecting data based on amost-likelihood, a decoder 17 for decoding data and outputtingreproduction data, a PLL (Phase Locked Loop) 18 for conducting a phasecomparison, a SUM/ID detector 19 for detecting address information, atiming counter and gate generator 50 for generating the timing and thegate signal to sample, a memory 51 for storing detected data, a memory52 for storing “0 (zero)” data only, a 1+D circuit 53 for generating aPR(1,1) waveform, a gain adjusting circuit 54 for adjusting crosstalkgain, a P/B (peak/bottom) detector 60 for detecting the peak and bottomof sample data, and the ODC (optical disk controller) 20 for controllingthe first reproduction circuit.

[0085] The reproduction signal in which the optical head 11 readsrecorded data on the recording medium 10 is amplified by amplifier 12and a high frequency noise is eliminated by the LPF 13. Then, thereproduction signal is supplied to the ADC 14.

[0086] Based on a reference clock CLK supplied from the PLL 18, thereproduction signal is sampled by the ADC 14 in response to a timingsupplied by the timing counter and gate generator 50. Sampled dataobtained by sampling the reproduction signal is equalized into apredetermined PR (Partial Response) by the EQ 15.

[0087] On the other hand, in order to recognize an address on whichinformation is recorded, the SUM/ID detector 19 detects the addressinformation by a SUM signal or a Wobble signal. Based on detectedaddress information, gate signal generated by the timing counter andgate generator 50 is supplied to the P/B detector 60.

[0088] The P/B detector 60 obtains differences between peak values andbottom values as signal amplitudes V_(A) and V_(B), respectively, inresponse to the gate signals Gate A and Gate B supplied from the timingcounter and gate generator 50. The P/B detector 60 obtains a crosstalkgain XTG_(A) (=V_(A)/V_(B)) showing an elimination ratio to thecrosstalk amount based on the signal amplitudes V_(A) and V_(B)obtained, and then supplies to the gain adjusting circuit 54.

[0089] The calculator 55 deducts the crosstalk gain XTG_(A) adjusted bythe gain adjusting circuit 54 from the sample value that is equalizedinto the PR waveform by the EQ 15. Then, the crosstalk is cancelled.

[0090] For the reproduction signal in which the crosstalk is canceled, amost likelihood is detected by the ML detector 16 and data is detectedbased on the detected most likelihood. Then, the decoder 17 decodes thedata.

[0091] When the ODC 20 conducts a crosstalk cancellation, the ODC 20switches a switch SW1 to the memory 51 in which the detected data of aprevious track is stored. On the other hand, when the crosstalkcancellation is conducted to realize a medium compatibility or thecrosstalk cancellation is not required because of a small amount of thecrosstalk, the switch SW1 is switched to the memory 52 in which only “0”is stored.

[0092] In a case in which a predetermined PR waveform, for example, aPR(1,1) waveform is synthesized from the detected data of the adjacenttrack stored in the memory 51, a 1+D operation (D indicates a delay forone clock) is conducted by the 1+D circuit 53 and then an ideal PRwaveform for the detected data is produced.

[0093] For example, when the data recorded on the data part 29 of thetrack T2n is decoded, first, the detected data, in which the datareproduction is conducted, of the data part 29 of the track T2n−1 isstored in memory 51.

[0094] Furthermore, when the target track T2n is reproduced, when thetarget track T2n is reproduced, the calculator 55 deducts the crosstalkgain XTG_(A) in which the gain adjustment is conducted, from thereproduction signal and then the crosstalk is cancelled. Thereproduction signal of the track T2n, in which the crosstalk iscanceled, is output as the reproduction data through the ML detector 16and the decoder 17. Moreover, the detected data, which is detected bythe ML detector 16, of the track T2n is stored in the memory 51 and thedetected data is used to cancel the crosstalk for the reproductionsignal of a next track.

[0095] Since the detected data detected by the ML detector 16 is storedin memory 51 every one bit, the crosstalk cancellation can be realizedin a smaller amount of memory than a case where the equalized samplevalue is stored.

[0096] The peak value and the bottom value are detected by the P/Bdetector 60 at timing as shown in FIG. 7.

[0097]FIG. 7 is a diagram showing a sampling example of the PR(1,1)waveform.

[0098] Referring to FIG. 7, the peak values and the bottom values aresampled at predetermined locations (at predetermined times) by using thepredetermined pattern. That is, the peak values are sampled at thepredetermined sampling times t=2, 6, 10, and 14, and the bottom valuesare sampled at the predetermined sampling times t=4, 8 and 12.

[0099] Moreover, in order to sample as shown in FIG. 7, the P/B detector60 is configured as shown in FIG. 8

[0100]FIG. 8 is a diagram showing an example of the circuitconfiguration of the peak bottom detector.

[0101] In FIG. 8, the P/B detector 60 includes a peak bottom differencecalculating circuit 75, a selector 66 for switching a V_(A) memory 67and a V_(B) memory 68 in response to a gate signal 74, the V_(A) memory67 for storing the signal amplitude V_(A), the V_(B) memory 68 forstoring the signal amplitude V_(B), a cancel gain calculating circuit 69for calculating crosstalk gain XTG_(A), and a XTG_(A) memory 70 forstoring crosstalk gain XTG_(A).

[0102] Furthermore, the peak bottom difference calculating circuit 75includes a selector 61 for distributing the sample value, a counter 62for counting the predetermined time t, a peak value averaging circuit 63for calculating an average of the peak value, a bottom value averagingcircuit 64 for calculating an average of the bottom value, and anaverage subtracting circuit 65 for calculating a difference betweenaverages of the peak value and the bottom value.

[0103] In the peak bottom difference calculating circuit 75, based onthe clock CLK supplied from the timing counter and gate generator 50 ofFIG. 6, the counter 62 counts a predetermined number and notifies theselector 61 of the timing for distributing the peak value or the bottomvalue. In response to the timing notified by the counter 62, theselector 61 distributes the sample value supplied from the EQ 15 to thepeak value averaging circuit 63 calculating the average of the peakvalue, or the bottom value averaging circuit 64 calculating the averageof the bottom value.

[0104] The peak value averaging circuit 63 calculates the average of thepeak value. Moreover, based on an average number set from the outside,the average of the peak value, in which a difference in a length of thepredetermined pattern and a difference in a signal quality are adjusted,is supplied to the average subtracting circuit 65.

[0105] The bottom value averaging circuit 64 calculates average of thebottom value. Moreover, based on an average number set from the outside,the average of the bottom value, in which a difference in the length ofthe predetermined pattern and the difference in the signal quality areadjusted, is supplied to the average subtracting circuit 65.

[0106] Based on the average obtained from each of the peak valueaveraging circuit 63 and the bottom value averaging circuit 64, theaverage subtracting circuit 65 calculates the average difference of peakvalue and a bottom value.

[0107] In response to the gate signal 74, the selector 66 distributesthe average difference from the peak bottom difference calculatingcircuit 75 as the signal amplitudes V_(A) or V_(B) to the V_(A) memory67 or the V_(B) memory 68.

[0108] The cancel gain calculating circuit 69 obtains the signalamplitudes V_(A) and V_(B) from the V_(A) memory 67 and the V_(B) memory68, calculates the crosstalk gain XTG_(A) (=V_(A)/V_(B)), and stores inXTG_(A) memory 70.

[0109] Therefore, by the gain adjusting circuit 54 of FIG. 6, thecrosstalk gain XTG_(A), in which the gain adjustment is conducted forthe PR signal, is deducted, and then the crosstalk is canceled.

[0110] In the above-desecribed method for canceling the crosstalk, twotracks are reproduced by one beam simultaneously; that is, an off-trackoperation is conducted. Accordingly, it is required to avoid a trackingerror when a track jump is conducted.

[0111] As a method for avoiding the tracking error caused by theoff-track when the track jump is conducted, for example, as shown inFIG. 9, the track jump is conducted at on-track and then is graduallypositioned at off-track.

[0112]FIGS. 9A, 9B, 9C, and 9D are diagrams showing a sequence exampleof the crosstalk cancel gain when the track jump is conducted.

[0113] Referring to FIG. 9A, in a case of the track jump, at a trackT2(n−1)−1 being one or more tracks inner side (or outer side), theoptical beam is positioned at a spot 90 at on-track by a kickback andthe recorded data is reproduced. At the kickback, the crosstalk cancelgain is set as “0 (zero).” That is, the memory 52 is selected by the ODC20 shown in FIG. 6.

[0114] In FIG. 9B, immediately after the track jump, the spot 90 is inthe state of the on-track at the track T2n−1, and then the spot 90 isgradually positioned to the off-track toward a track T2(n+1)−1.

[0115] In a state immediately after the track jump in FIG. 9B, the spot90 is still at the on-track. Thus, the crosstalk cancel gain stillindicates “0 (zero)”. Also, an offset for the tracking error signal(TES) is “0 (zero)”.

[0116] The offset is determined using the tracking error signals at thekickback and immediately after the track jump.

[0117] Referring to FIG. 9C, in a case in which a next track T2n isreproduced while approaching toward a target track T2(n+1)−1, the offsetdetermined for the tracking error signal is conducted, and the crosstalkcancel gain is defined, for example, as “0.5”.

[0118] Referring to FIG. 9D, in a case in which the target trackT2(n+1)−1 is successively reproduced, similarly to the case ofreproducing the track T2n, the offset determined for the tracking errorsignal is conducted, and the crosstalk cancel gain is defined, forexample, as “1”.

[0119] Thus, the crosstalk cancel gain is gradually magnified toward thetarget track T2(n+1)−1, and the crosstalk cancel gain is magnified moreas the accuracy of reproduction data becomes higher. An off-track amountis also magnified gradually. Therefore, it is possible to avoidconducting the crosstalk cancellation to the detected data at the trackjump of an earlier stage in which many data errors occur. As describedabove, in the crosstalk cancellation according to the embodiment of thepresent invention, it is possible to avoid conducting the datareproduction that accelerates a data error.

[0120]FIG. 10 is a diagram showing a relationship between a successivetrack reproduction number, and the crosstalk cancel gain.

[0121] As appreciated from FIG. 10, the crosstalk cancel gain isgradually increasing from “0 (zero)” until the successive trackreproduction number becomes five and the crosstalk cancel gain becomes“1” where the successive track reproduction number is more than five.

[0122] Thus, after the crosstalk cancel gain becomes “1”, the crosstalkcancel gain remains “1”.

[0123] A method for improving a reproduction process in speed will nowbe described in which a memory is provided to each sector.

[0124]FIG. 11 is a diagram showing an optical hard disk format.

[0125] A CAV (Constant Angular Velocity) disk such as shown in FIG. 11includes twelve sectors, each of which has a header part and a datapart, on each track.

[0126] For example, a second reproduction circuit, which corresponds toa format of the CAV disk and realizes higher speed, can be configured asshown in FIG. 12.

[0127] In a case of an MCAV, the crosstalk signal memory is providedonly for each of outer tracks having a greater number of sectors thaninner tracks.

[0128]FIG. 12 is a diagram showing a configuration example of the secondreproduction circuit. In FIG. 12, circuits that are the same as the onesin FIG. 6 are indicated by the same reference numerals and theexplanation thereof will be omitted. Moreover, a portion 151 surroundedby a dotted line shows a characteristic configuration in the secondreproduction circuit.

[0129] Referring to FIG. 12, the second reproduction circuit includesthe optical head 11 for reading recorded data in the recording medium10, the amplifier 12 for amplifying the reproduction signal, the LPF 13for eliminating high frequency noise, the ADC 14 for converting thereproduction signal into digital data, the EQ 15 for equalizing to apredetermined waveform, the calculator 55 for deducting the crosstalkfrom the reproduction signal, the ML detector 16 for detecting databased on the degree, the decoder 17 for decoding data and outputtingreproduction data, the PLL (Phase Locked Loop) 18 for conducting a phasecomparison, the SUM/ID detector 19 for detecting address information,the timing counter and gate generator 50 for generating the timing andthe gate signal to sample, memories 101 through 112 for storing detecteddata, the memory 52 for storing “0 (zero)” data only, the 1+D circuit 53for generating the PR(1,1) waveform, the gain adjusting circuit 54 foradjusting crosstalk gain, the P/B (peak/bottom) detector 60 fordetecting the peak and bottom of sample data, and the ODC (optical diskcontroller) 20 for controlling the second reproduction circuit.

[0130] In the second reproduction circuit shown in FIG. 12, instead ofthe memory 51 shown in FIG. 6, the memories 101 through 112 are providedfor twelve sectors of one track, the ODC 20 controls switches SW2 andSW3 and switches to one of the memories.

[0131] The detected data detected from each sector is stored in each ofthe memories 101 through 112, and the detected data is used to cancelthe crosstalk. The same method for canceling crostalk as that of thefirst reproduction circuit shown in FIG. 6 can be applied.

[0132] Thus, it is possible to conduct the reproduction process for aplurality of tracks in a shorter time.

[0133] Moreover, in a case in which a plurality of memories are providedfor all tracks for each sector, for example, as shown in FIG. 13, thesame number of memories as the number of tracks are further provided ina single memory for each sector.

[0134]FIG. 13 is a diagram showing a memory configuration example insidethe single memory for each sector.

[0135] Referring to FIG. 13, for example, the memory 101 shown in FIG.12 includes a set of memories 101-01, 101-02, . . . , 101-(x−1), 101-xcorresponding to tracks Ti through Tx, respectively. Switches SW4 andSW5 are controlled by the ODC 20 and then one of the memories 101-01,101-02, . . . , 101-(x−1), 101-x is switched.

[0136] Thus, it is possible to conduct the reproduction process athigher speed by providing the memories 101-01, 101-02, . . . ,101-(x−1), 101-x in a track direction (a radius direction).

[0137] Since the detected data detected by the ML detector 16 are storedin the memories shown in FIG. 12 and FIG. 13, it is possible to reduce amemory amount less than a case of storing the sample values for eachsector or each track.

[0138] For example, in a case of using a code having a longer lengthafter encoded than before encoded such as a run length limited code, forexample, (1,7)RLLC, (2,7)RLLC or a like, a third reproduction circuit isconfigured as shown in FIG. 14, so as to cancel the crosstalk.

[0139]FIG. 14 is a diagram showing a configuration example of the thirdreproduction circuit. In FIG. 14, circuits that are the same as the onesin FIG. 6 are indicated by the same reference numerals and theexplanation thereof will be omitted. Moreover, a portion 152 surroundedby a dotted line shows a characteristic configuration in the thirdreproduction circuit.

[0140] Referring to FIG. 14, the third reproduction circuit includes theoptical head 11 for reading recorded data in the recording medium 10,the amplifier 12 for amplifying the reproduction signal, the LPF (lowpass filter) 13 for eliminating high frequency noise, the ADC (A/Dconverter) 14 for converting the reproduction signal into digital data,the EQ 15 for equalizing to a predetermined waveform, the calculator 55for deducting the crosstalk from the reproduction signal, the MLdetector 16 for detecting data based on a most-likelihood, the decoder17 for decoding data and outputting reproduction data, the PLL (PhaseLocked Loop) 18 for conducting a phase comparison, the SUM/ID detector19 for detecting address information, the timing counter and gategenerator 50 for generating the timing and the gate signal to sample, anencoder 80 for encoding decoded data, a NRZ1 (Non-Return-to-Zero)circuit 81 for converting into a LD (laser diode) drive signal, thememory 52 for storing “0 (zero)” data only, the 1+D circuit 53 forgenerating the PR(1,1) waveform, the gain adjusting circuit 54 foradjusting crosstalk gain, the P/B (peak/bottom) detector 60 fordetecting the peak and bottom of sample data, and the ODC (optical diskcontroller) 20 for controlling third reproduction circuit.

[0141] In the third reproduction circuit shown in FIG. 14, in order tocorrespond to data to be sampled, the encoder 80 for encoding decodeddata, and the NRZ1 circuit 81 for changing decoded data into a LD drivesignal are provided to produce the crosstalk waveform.

[0142] Therefore, even in a case of using decoded data having a shorterdata length than the sample data of the reproduction signal, it ispossible to realize a smaller memory amount and to cancel the crosstalk.

[0143] Moreover, in a case in which corrected data, which an error ofdata is corrected by an ECC (Error Correcting Code), is stored in thememory 51, a fourth reproduction circuit is configured shown in FIG. 15,so that the crosstalk can be cancelled.

[0144]FIG. 15 is a diagram showing a configuration example of the fourthreproduction circuit. In FIG. 15, circuits that are the same as the onesin FIG. 14 are indicated by the same reference numerals and theexplanation thereof will be omitted. Moreover, a portion 153 surroundedby a dotted line shows a characteristic configuration in the fourthreproduction circuit.

[0145] Referring to FIG. 15, the fourth reproduction circuit includesthe optical head 11 for reading recorded data in the recording medium10, the amplifier 12 for amplifying the reproduction signal, the LPF(low pass filter) 13 for eliminating high frequency noise, the ADC 14for converting the reproduction signal into digital data, the EQ 15 forequalizing to a predetermined waveform, the calculator 55 for deductingthe crosstalk from the reproduction signal, the ML detector 16 fordetecting data based on a most-likelihood, the decoder 17 for decodingdata and outputting reproduction data, the PLL (Phase Locked Loop) 18for conducting a phase comparison, the SUM/ID detector 19 for detectingaddress information, the timing counter and gate generator 50 forgenerating the timing and the gate signal to sample, an encoder 82 forencoding decoded data including the ECC, a NRZ1 (Non-Return-to-Zero)circuit 81 for converting into the LD (laser diode) drive signal, the1+D circuit 53 for generating the PR(1,1) waveform, the gain adjustingcircuit 54 for adjusting the crosstalk gain, the P/B (peak/bottom)detector 60 for detecting the peak and bottom of the sample data, and anODC (optical disk controller) 201 for controlling the fourthreproduction circuit. The ODC 201 further includes an ECC 202.

[0146] In the fourth reproduction circuit shown in FIG. 15, correcteddata, in which an error is corrected by the ECC 202, is stored in thememory 51. After that, the same reproduction process as the thirdreproduction circuit shown in FIG. 14 is conducted. Thus, it is possibleto cancel the crosstalk from the reproduction signal.

[0147] Since the corrected data, in which the error is corrected by theECC 202, is stored in the memory 51, it is possible to avoid includingan error in the crosstalk signal produced.

[0148] A third format in a case of producing the crosstalk signal usingthree tracks will now be described.

[0149]FIG. 16 is a diagram showing an example of the third format.

[0150] Referring to FIG. 16, such as the first format shown in FIG. 3,the predetermined signal, for example, 2T-repeated data 94 is shifted inthe measuring area for measuring the crosstalk for each track in threetracks so as to form a stagger. In the third format shown in FIG. 16,one beam irradiates simultaneously three tracks T3n−1, T3n, and T3n+1like a spot 93.

[0151] A fifth reproduction circuit, in which the crosstalk is cancelledwhile data recorded in accordance with the third format forming thestagger as shown in FIG. 16, will now be described with reference toFIG. 17.

[0152]FIG. 17 is a diagram showing a configuration example of the fifthreproduction circuit. In FIG. 17, circuits that are the same as the onesin FIG. 6 are indicated by the same reference numerals and theexplanation thereof will be omitted. Moreover, a portion 154 surroundedby a dotted line shows a characteristic configuration in the fifthreproduction circuit.

[0153] Referring to FIG. 17, the fifth reproduction circuit includes theoptical head 11 for reading recorded data in the recording medium 10,the amplifier 12 for amplifying the reproduction signal, the LPF (lowpass filter) 13 for eliminating high frequency noise, the ADC (A/Dconverter) 14 for converting the reproduction signal into digital data,the EQ 15 for equalizing to a predetermined waveform, a memory 211 forstoring the sample data reproduced, a calculator 551 for deducting thecrosstalk from the regenerative signal, the ML detector 16 for detectingdata based on a most-likelihood, the decoder 17 for decoding data andoutputting reproduction data, the PLL (Phase Locked Loop) 18 forconducting a phase comparison, the SUM/ID detector 19 for detectingaddress information, a timing counter and gate generator 501 forgenerating the timing and the gate signal for sampling, memories 511 and512 for storing the detected data, the memory 52 for storing “0 (zero)”data only, 1+D circuits 531 and 532 for generating the PR(1,1) waveform,gain adjusting circuits 541 and 542 for adjusting crosstalk gains, a P/B(peak/bottom) detector 601 for detecting the peak and the bottom of thesample value, and an ODC (optical control circuit) 210 for controllingthe fifth reproduction circuit.

[0154] Based on the address information detected by the SUM/ID detector19, the timing counter and gate generator 501 generates gate signals asa gate A corresponding to a previous track that is before the targettrack, a gate B corresponding to the target track to be reproduced, anda gate C corresponding to a next track that is after the target track.

[0155] The P/B detector 601 obtains the signal amplitude V_(A), V_(B),and V_(C) in accordance with the gate signal supplied from the timingcounter and gate generator 501, by calculating differences between thepeak values and the bottom values, respectively. Furthermore, based onthe signal amplitude VA, VB, and VC, the P/B detector 601 obtainscrosstalk gains XTG_(A) (=V_(A)/V_(B)) and XTG_(C) (=V_(A)/V_(C)) andsupplies to the gain adjusting circuits 541 and 542, respectively.

[0156] In a case in which a track T3n is the target track, in order toconduct the crosstalk cancellation, the ODC 210 stores the detected dataof the track T3n−1 corresponding to the gate A in the memory 511 byswitching a switch SW12, and controls to store the detected data of atrack T3n+1 corresponding to the gate C in the memory 512. On the otherhand, in a case in which the crosstalk cancellation is not conducted,the ODC 210 switches switches SW13 and SW14 to the memory 52 storing “0”only. Moreover, the ODC 210 controls the switch SW11 and enables thecalculator 551 to obtain the sample data that is reproduced, from thememory 211.

[0157] The 1+D circuits 531 and 532 produce the ideal PR waveforms fordata stored in memories 511 and 512, respectively, by conducting a 1+Dprocess (delay by one clock).

[0158] The gain adjusting circuits 541 and 542 adjust the gain of thecrosstalk gain XTG_(A) and XTG_(C), and supply to the calculator 55.

[0159] The calculator 551 cancels the crosstalk of the track T3n bydeducting one crosstalk signal from the previous track T3n−1 and anothercrosstalk signal from the next track T3n+1, from the reproduction signalfrom the target track T3n.

[0160]FIG. 18 is a diagram showing an effect of the crosstalkcancellation.

[0161] Referring to FIG. 18, in a case in which the crosstalk iscancelled according to the embodiment as described above, compared withanother case in which the crosstalk is not cancelled, for example, evenif the crosstalk amount increases by 15 dB from −30 dB to −15 dB, datacan be reproduced at the same bit error rate as a case in which nocrosstalk occurs.

[0162] In the embodiment as described above, data recorded on the targettrack and the adjacent tracks are reproduced by one beam and the sampleddata of the reproduction signal is stored in the memories. The detecteddata processed by the ML detector 16 is stored the memories 511 and 512as the reproduction signal of the adjacent track, so as to use as acancel signal.

[0163] Since the detected data to store can be set to “0 (zero)” or “1”,it is possible to produce a crosstalk signal by synthesizing with a PRcharacteristic. In this case, instead of storing the sample value afterprocessed by the ADC 14 and the EQ 15, a one-bit data string is storedin the memories 511 and 512. Therefore, it is possible to reduce thememory aount.

[0164] Moreover, the measurement area of crosstalk is provided and thepredetermined signal for measuring crosstalk (for example, the2T-repeated signal) is provided to form a stagger. Thus, it is possibleto prevent the crosstalk from occurring from the adjacent tracks. As themeasurement area, the existing areas (for example, the Read Clock PhaseControl Area or the like) of the conventional format are used. That is,the existing area forms the measurement area of the crosstalk so as toshift for the adjacent tracks and a shifted portion is used as a bufferarea.

[0165] In the measurement area, data is sampled in response to the gatesignal sent from the timing counter and gate generator 50 or 501.

[0166] The sample value is classified into a peak point and a bottompoint, and values at the peak point and the bottom point are averaged soas to obtain the peak value and the bottom value. By externally definingthe average number, it is possible to control a range for obtaining thecrosstalk cancel gain to be narrower or wider in order to correspond toany format for recording data.

[0167] Therefore, the crosstalk cancel gain can be varied and also thecrosstalk cancel gain can be measured when data is reproduced.

[0168] Since the ODCs 20, 201 and 210 selects the memory 52 storing “0”only not to produce the crosstalk signal while processing the crosstalkcancellation, it is possible to conduct a crosstalk cancellation-offoperation.

[0169] Furthermore, the crosstalk amount in the measurement area of thepredetermined pattern can be measured by the cancellation-off operation.

[0170] In a case in which the track jump is conducted, data recorded onthe adjacent track is reproduced while tracking from one or more tracksinner (or outer) than the target track, and then data recorded on thetarget track is gradually reproduced. At a first track when the trackjump is conducted, the recorded data is reproduced without conducting anoff-track. The off-track is conducted from the next track to reproducetwo tracks simultaneously, and the crosstalk is cancelled to properlyreproduce the recorded data. After the track jump, the crosstalk cancelgain is set to “0” for the first track and then the crosstalk cancelgain is gradually increased. When the crosstalk cancel gain becomes “1”,the crosstalk cancel gain maintains “1”. Consequently, it is possible toproperly avoid a data error when the track jump is conducted.

[0171] The reproduction process at higher speed can be realized byproviding a plurality of memories corresponding to a sector number ofone track (in circumferential direction).

[0172] Alternatively, the reproduction process at higher speed can berealized by providing a plurality of memories corresponding to a tracknumber in a radius direction.

[0173] In the method for canceling the crosstalk in the embodimentdescribe above, the crosstalk signal generated from at least oneadjacent track is deducted from the reproduction signal when the datapart (MO part) recorded on the recording medium 10 is reproduced. Next,a method for canceling the crosstalk in a case of reproducing an addresspart (pre-pit part) will now be described.

[0174]FIG. 19 is a diagram showing a spot position of the optical beamwhen the address part is reproduced. In FIG. 19, for example, in a casein which the track T2n (n denotes a natural number) is reproducedsimilar to the case of reproducing the data part, the optical beamsimultaneously irradiates two tracks of the track T2n−1 and the trackT2n by a spot 240 shifting toward the adjacent track T2n−1, and thepre-pit parts showing addresses i+m and i are read. In this case,differently from the data part, the address i+m of the adjacent trackT2n−1 is known. For example, as shown in FIG. 20, circuits can beconfigured so as to directly generate the crosstalk from the addressi+m.

[0175]FIG. 20 is a diagram showing a configuration example of a sixthreproduction circuit. Referring to FIG. 20, the sixth reproductioncircuit includes the optical head 11 for reading recorded data in therecording medium 10, the amplifier 12 for amplifying the reproductionsignal, the LPF (low pass filter) 13 for eliminating high frequencynoise, the ADC (A/D converter) 14 for converting the reproduction signalinto digital data, the EQ (digital equalizer) 15 for equalizing to apredetermined waveform, the calculator 55 for deducting the crosstalkfrom the reproduction signal, the ML detector 16 for detecting databased on a most-likelihood, the decoder 17 for decoding data andoutputting reproduction data, a PLL (Phase Locked Loop) 6011 forconducting a phase comparison, the timing counter and gate generator 50for generating the timing and the gate signal to sample, a 1+D circuit602 for generating the PR(1,1) waveform, a gain adjusting circuit 603for adjusting the crosstalk gain, a crosstalk gain calculator 600 fordetecting the peak value and bottom value of the sample data andcalculating the crosstalk gain showing a crosstalk elimination ratio,and an ODC (optical disk controller) 620 for controlling the sixthreproduction circuit.

[0176] The reproduction signal which read recorded data in the recordingmedium 10 by the optical head 11 is amplified by the amplifier 12, highfrequency noise is eliminated by the LPF 13, and then the reproductionsignal is supplied to the ADC 14.

[0177] Based on the reference clock CLK supplied from the PLL 6011, inresponse to the timing provided by the timing counter and gate generator50, the reproduction signal is sampled by the ADC 14. The sample valueobtained by sampling is equalized into a desired PR (Partial Response)waveform by the EQ 15. Then, data is detected based on the PR waveformby the ML decoder 16, and decoded and output by the decoder 17.

[0178] In order to lead sampling data from ADC 14 at high speed whenleading into the PLL 6011, a switch SW21 provided to the PLL 6011 isswitched to the ADC 14. And the switch SW21 is switched to the EQ 15 inorder to synchronize using data so that the data from the EQ 15 isproperly sampled as expected by the PRML after leading the samplingdata. A switching timing is controlled by the ODC 620 or a countersimilar to the ODC 620.

[0179] In a case in which the ODC 620 conducts the crosstalkcancellation, for example, in a case in which the track T2n isreproduced as shown in FIG. 19, the ODC 620 supplies a signal showingthe address i+m of the adjacent track T2n−1 as an adjacent ID signal tothe 1+D circuit 602. Moreover, when the track jump is conducted, the ODC620 supplies all “0 (zero)” not to conduct the crosstalk cancellation.The ODC 620 controls a switch SW21 of the PLL 6011.

[0180] For example, in a case in which the track T2n is reproduced asshown in FIG. 19, the crosstalk gain calculator 600 calculates thecrosstalk gain based on a phase difference between the track T2n and theadjacent track T2n−1, and supplies to the gain adjusting circuit 603. Ina case of synthesizing a predetermined PR waveform based on the adjacentID signal supplied by the ODC 620, for example, in a case ofsynthesizing the PR(1,1) waveform, the 1+D circuit 602 conducts the 1+Dprocess (delay for one clock) and for example, produces the ideal PRwaveform for the address i+m adjacent to the track T2n. The gainadjusting circuit 603 adjusts the ideal PR waveform produced by the 1+Dcircuit 602 based on the crosstalk gain calculated by the crosstalk gaincalculator 600.

[0181] The calculator 55 deducts the crosstalk gain adjusted by the gainadjusting circuit 603 from the sample value equalized into the PRwaveform by the EQ 15. Thus, the crosstalk is cancelled. Amost-likelihood is detected from the reproduction signal, in which thecrosstalk is cancelled, by the ML detector 16, data is detected based onthe most-likelihood, and the data is decoded by the decoder 17.

[0182]FIG. 21A is a diagram showing a record example of the pre-pit.Referring to the record example of the pre-pit shown in FIG. 21A, forexample, in the pre-pit part (address part) of the track T2n−1, an IDinformation showing the address i+m is recorded after a predeterminedpattern. The predetermined pattern is formed by recording the2T-repeated data (2T convex part) at 2T interval (2T concave part) andthe 8T-repeated data (8T convex part) twice at 8t interval (8T concavepart). Moreover, in the pre-pit part of the track T2n, the 2T-repeateddata is recorded four times at 2T interval and the 2T-repeated data isfurther recorded once so as to shift the predetermined pattern. Then,similarly to the track T2n−1, the ID information showing the address iis recorded after the predetermined pattern. Consequently, thepredetermined pattern is recorded so as to shift by 4T from the adjacenttrack.

[0183]FIG. 21B is a diagram showing the reproduction signal of the trackT2n−1 only and FIG. 21C is a diagram showing the reproduction signal ofthe track T2n only. Referring to FIG. 21B and FIG. 21C, amplitude of thereproduction signal is higher at the convex part recording data and islower at the concave part of interval. The predetermined pattern isformed at a record position so that a phase of the reproduction signalof the track T2n delays by 2T.

[0184]FIG. 21D is a diagram showing a synthesized reproduction signal ofthe track T2n−1 and the track T2n. Referring to FIG. 21D, in a case inwhich two reproduction signals causes the crosstalk at one-to-one ratiowhen the optical beam scans the track T2n−1 and the track T2nsimultaneously as shown in FIG. 19, the reproduction signals shown inFIG. 21B and FIG. 21C are synthesized to form a synthesized reproductionsignal. That is, referring to FIG. 21D, the amplitude of the synthesizedreproduction signal becomes “2” in the 2T-repeated data part and a leveldifference is formed on the waveform of the synthesized reproductionsignal in the 8T-repeated data part. The crosstalk amount is obtainedusing the level difference on the waveform of the synthesizedreproduction signal.

[0185]FIG. 22 is a diagram showing an example of waveform change causedby the crosstalk amount and a phase shift. Referring to a correspondencetable of FIG. 22, the waveform change of an interference-wave, which iscaused by the crosstalk amount and the phase shift from the adjacenttrack (for example, the track T2n−1) at the predetermined pattern, isshown. The crosstalk amount is shown by a ratio (logarithm of [signal ofthe track T2n−1]/[signal of the track T2n] ratio (hereinafter, calledT2n−1/T2n ratio)) of signals from the track T2n−1 and the track T2n.When the crosstalk amount is changed, the amplitude of the synthesizedreproduction signal is changed. In this case, the amplitude iscontrolled by an AGC (Auto Gain Control) so as to be constant. In FIG.22, it is shown that the T2n−1/T2n ratio showing the crosstalk amountbecomes higher when a center of the optical beam shifts more toward aside of the track T2n−1 and the crosstalk amount becomes lower when thecenter of the optical beam shifts more toward a side of the track T2n.Also, in FIG. 22, as a phase shift sate, three states of a “4T−25% phaseshift of T2n” state, a “4T phase shift of T2n” state, and a “4T+25%phase shift of T2n” state are shown. The “4T−25% phase of T2n” stateshows that the phase of the track T2n is ahead by a 4T−25% phase fromthe phase of the track T2n−1. The “4T phase shift of T2n” state showsthat the phase of the track T2n is shifted by a predetermined 4T phasefrom the track T2n−1. The “4T+25% phase shift of T2n” state shows thatthe phase of the track T2n is delayed from the phase of the track T2n−1.For example, a waveform in which the T2n−1/T2n ratio showing thecrosstalk amount indicates “0 (zero)” dB and the phase shift between thetrack T2n−1 and the track T2n indicates the “4T phase shift of T2n”state, corresponds to the synthesized reproduction signal shown in FIG.21D.

[0186] Based on each waveform corresponding to the crosstalk amount andthe phase shift, the reproduction signal is sampled and an amplituderatio is calculated by amplitude (Sp−Sb) in the predetermined patternpart and the level difference (Sy−Sz) where the amplitude is changed bythe crosstalk, so that the crosstalk amount for canceling the crosstalkcan be obtained. It should be noted that a reference numeral Spindicates a peak value and a reference numeral Sb indicates a bottomvalue.

[0187]FIG. 23 is a diagram showing a relationship between the amplituderatio and the crosstalk amount. Referring to FIG. 22, for example, in awaveform in which the T2n−1/T2n ratio is 0 (zero) dB in any one of the“4T−25% phase shift of T2n” state, the “4T phase shift of T2n” state,and the “4T+25% phase shift of T2n” state, the amplitude difference(Sy−Sz) is approximately 0 (zero) dB. Thus, the amplitude ratio isapproximately 0 (zero) dB. Referring to FIG. 23, the crosstalk amountfor the amplitude ratio (gain) “0 (zero)” shows “0 (zero)”. Thus, thesame result as that shown in the correspondence table of FIG. 22 can beobtained. Also, in any waveform in the “4T−25% phase shift of T2n”state, the “4T phase shift of T2n” state, and the “4T+25% phase shift ofT2n” state, the larger negative the amplitude difference (Sy−Sz) becomes(that is, the optical beam shifts to track T2n−1 side), the largerpositive the amplitude (Sp−Sb) of the predetermined pattern partbecomes. Consequently, the crosstalk amount to be canceled is positivelyincreased. On the other hand, even in any waveform in in the “4T−25%phase shift of T2n” state, the “4T phase shift of T2n” state, and the“4T+25% phase shift of T2n” state, the greater positive the amplitudedifference (Sy−Sz) becomes (that is, the optical beam shifts to trackT2n side), the greater negative the crosstalk amount to be cancelledbecomes. Accordingly, the same result oas that shown in thecorrespondence table of FIG. 22 can be obtained.

[0188] Therefore, it is possible to obtain the crosstalk amount forchange of the waveform shown in FIG. 22 by the relationship between theamplitude ratio and the crosstalk amount shown in FIG. 23.

[0189] Next, a circuit configuration of the crosstalk gain calculator600 for calculating the crosstalk gain based on the relationship shownin FIG. 23.

[0190]FIG. 24 is a diagram showing a circuit configuration example ofthe crosstalk gain calculator. The crosstalk gain claculator 600 shownin FIG. 20 includes an amplitude value calculating circuit 610 forobtaining an average of the amplitude (Sp−Sb) in the predeterminedpattern part and an average of the amplitude (Sy−Sz) changed by thecrosstalk, a selector 631 for selecting a memory in response to a gatesignal, a Sy−Sz memory 632 for storing the amplitude (Sy−Sz) changed bythe crosstalk, a Sp−Sb memory for storing the amplitude (Sp−Sb) in thepredetermined pattern part, a map 634 having a relationship table asshown in FIG. 23, a decoder 635 for obtaining the crosstalk amount fromthe amplitude ration by referring to the map 634, and an XTG memory 636for storing the crosstalk gain. In addition, the amplitude valuecalculating circuit 610 includes a counter 611 for counting a clock CLK,a selector 612 for selecting Sy, Sp, Sz, or Sb by counting the samplevalue by the clock CLK, an averaging circuit 613 for averaging Sy or Spbased on an average number, an averaging circuit 614 for averaging Sz orSb based on an average number, and a subtractor 615 for calculating anaverage difference of the averages calculated by the averaging circuit613 and the averaging circuit 614.

[0191] The amplitude value calculating circuit 610 calculates an averagevalue of sample value Sy by the averaging circuit 613 and alsocalculates an average value of sample value Sz by the averaging circuit614. In response to the gate signal, the sample values Sy and Sz aresupplied from the selector 612 to the amplitude value calculatingcircuit 610 every predetermined count number. A value resulted insubtracting the average value of the sample value Sz the average valueof the sample value Sy is supplied to the selector 631 by the subtractor615. Moreover, the amplitude value calculating circuit 610 an averagevalue of sample value Sp by the averaging circuit 613 and alsocalculates an average value of sample value Sb by the averaging circuit614. In response to the gate signal, the sample values Sp and Sb aresupplied from the selector 612 to the amplitude value calculatingcircuit 610 every predetermined count number. A value resulted insubtracting the average value of the sample value Sb the average valueof the sample value Sp is supplied to the selector 631 by the subtractor615.

[0192] The selector 631 selects the Sy−Sz memory 632 or the Sp−Sz memory633 in response to the gate signal, in order to store the average valuesupplied from the amplitude value calculating circuit 610. The decoder635 calculates the amplitude ratio ((Sy−Sz)/(Sp−Sz)) based on theaverage value stored in the Sy−Sz memory 632 or the Sp−Sz memory 633,obtains the crosstalk amount for the amplitude ration by referring tothe map 634, and stores the crosstalk amount as the crosstalk gain inthe XTG memory 636. The XTG memory 636 supplies the corsstalk gain tothe gain adjusting circuit 603 shown in FIG. 20 in response to the gatesignal.

[0193] As described above, it is-possible to cancel the crosstalksignal, without providing an extra memory area in a direction ofarranging the bits in the pre-pit part on the recording medium 10 suchas conventional format.

[0194] Without degrading the format effect in the address informationarea, it is possible to cancel the crosstalk of the address signal.Moreover, since the track density can be improved higher, the formateffect is improved and then the record density can be improved.

[0195] In the embodiment, the memory 51 in FIG. 6 corresponds to astoring part, the 1+D circuit 53 corresponds to a crosstalk signalgenerating part, and the calculator 55 corresponds to a crosstalk signaleliminating part.

[0196] As describe above, according to the present invention, thecrosstalk signal from the adjacent track is generated and then thecrosstalk signal can be eliminated from the target reproduction signalfrom the target track to be reproduced. Therefore, it is possible toimprove the quality of the reproduction signal from data recorded on therecording medium in which tracks are formed at high density. Inaddition, since the detected data detected in accordance with thepredetermined algorithm is stored and also the detected data is a bitvalue, it can be realized to eliminate the crosstalk by less storagearea.

[0197] Moreover, according to the present invention, the predeterminedmeasurement data is recorded on the recording medium and a precisecrosstalk amount can be obtained by reading the measurement data. Inaddition, it is possible to variably eliminate the crosstalk signal fromthe reproduction signal by the crosstalk elimination ratio.

[0198] The present invention is not limited to the specificallydisclosed embodiments, variations and modifications, and othervariations and modifications may be made without departing from thescope of the present invention.

[0199] The present application is based on Japanese Priority ApplicationNo.2001-288470 filed on Sep. 21, 2001, the entire contents of which arehereby incorporated by reference.

What is claimed is:
 1. An apparatus for reproducing recorded data bydecoding a reproduction signal read from the recorded data recorded on arecording medium in accordance with a predetermined algorithm, saidapparatus comprising: a crosstalk signal generating part generating acrosstalk signal by converting adjacent data recorded on an adjacenttrack into a waveform of said reproduction signal; and a crosstalksignal eliminating part eliminating said crostalk signal by deductingfrom said reproduction signal, wherein said reproduction signal in whichsaid crosstalk signal is eliminated is decoded in accordance with saidpredetermined algorithm and reproduced.
 2. The apparatus as claimed inclaim 1, further comprising a storing part having at least one memoryand storing detected data detected by said predetermined algorithm whensaid recorded data is user data, wherein said crosstalk signalgenerating part generates said crosstalk signal by converting saiddetected data stored in said storing part into said waveform of saidreproduction signal, and said reproduction signal showing said userdata, in which said crosstalk signal is eliminated by said crosstalksignal eliminating part, is decoded by said predetermined algorithm andreproduced.
 3. The apparatus as claimed in claim 2, further comprising:a measurement data recording part recording a predetermined measurementdata to measure a crosstalk amount; and an elimination ratio obtainingpart obtaining the crosstalk amount based on said measurement data readfrom said recording medium and obtaining a crosstalk elimination ratio,wherein said crosstalk signal generated by said crosstalk signalgenerating part is eliminated from said reproduction signal based onsaid crosstalk elimination ratio.
 4. The apparatus as claim in claim 3,wherein said measurement data recording part records said measurementdata so as to shift from said measurement data recorded on said adjacenttrack.
 5. The apparatus as claimed in claim 3, wherein said measurementdata recording part records a predetermined data as the measurement dataso as to shift from recording positions of an area for recording saidpredetermined data and a buffer area in a header part of the recordeddata, so that one of said recording positions is shifted for saidmeasurement data recorded on said adjacent track.
 6. The apparatus asclaimed in claim 3, further comprising a gate signal generating partgenerating a gate signal in response to reading said measurement data,wherein said elimination ratio obtaining part obtains a first crosstalkamount based on the reproduction signal from at least one adjacent trackand a second crosstalk amount based on the reproduction signal from atarget track to be reproduced in response to said gate signal generatedby said gate signal generating part, and obtains said corsstalkelimination ratio.
 7. The apparatus as claimed in claim 3, wherein saidelimination ration obtaining part comprises: a peak average valuecalculating part calculating an average of peak values of saidreproduction signal of said measurement data; a bottom average valuecalculating part calculating an average of bottom values of saidreproduction signal of said measurement data; and an average valuecalculating part calculating a difference between the average values ofsaid peak values and said bottom values, so as to obtain said crosstalkelimination ratio by defining said difference as said crosstalkelimination ratio.
 8. The apparatus as claimed in claim 7, wherein saidpeak average value calculating part and said bottom peak average valuecalculating part calculate said average of said peak values and saidaverage of said bottom values based on a value number externallydefined.
 9. The apparatus as claimed in claim 6, wherein saidelimination ratio obtaining part obtains said crosstalk eliminationratio by dividing said first crosstalk amount based on said measurementdata read from said adjacent track by said second crosstalk amount basedon said measurement data read from said target track.
 10. The apparatusas claimed in claim 2, further comprising a zero data storing partstoring zero data only wherein said crosstalk signal generating partobtains said zero data from said zero data storing part when saidcrosstalk signal is not generated.
 11. The apparatus as claimed in claim2, wherein said storing part comprises sector memories for a number ofsectors so as to store said detected data detected in accordance withsaid predetermined algorithm for each sector.
 12. The apparatus asclaimed in claim 11, wherein each of said sector memories includes trackmemories for a number of tracks so as to said detected data detected inaccordance with said predetermined algorithm for each sector for eachtrack.
 13. The apparatus as claimed in claim 2, further comprises a readsignal converting part converting decoded data into a read signal forreading said recorded data recorded on said recording medium, whereinsaid storing part stores said decoded data, said read signal convertingpart converts said decoded data stored by said storing part into saidread signal, and said crosstalk signal generating part converts saidread signal converted by said read signal converting part into saidwaveform of said reproduction signal.
 14. The apparatus as claimed inclaim 13, wherein said read signal converting part comprises: anencoding part encoding data; and a non-return-to-zero circuit convertingsaid data encoded by said encoding part.
 15. The apparatus as claimed inclaim 2, further comprising a read signal converting part convertingcorrected data into said read signal for reading said recorded datarecorded on said recording medium, wherein said storing part convertssaid corrected data stored by said storing part into said read signaland said crosstalk signal generating part converts said read signalconverted by said read signal converting part into said waveform of saidregeneration signal.
 16. The apparatus as claimed in claim 2, furthercomprising a read controlling part controlling to read said recordeddata recorded on a target track to be reproduced by an off-track,wherein said crosstalk signal eliminating part eliminates an actualcrosstalk signal caused by said off-track from one side of an adjacenttrack, by deducting said crosstalk signal generated by said crosstalksignal generating part from said reproduction signal.
 17. The apparatusas claimed in claim 16, wherein said read controlling part controls tojump a track located at one or more tracks distant from a target trackto be reproduced when a track jump is conducted and conducts areproduction process for said target track by an on-track.
 18. Theapparatus as claimed in claim 17, wherein said read controlling partcontrols to jump a landing track by the on-track when the track jump isconducted.
 19. The apparatus as claimed in claim 16, wherein saidelimination ratio obtaining part sets zero as said crosstalk eliminationratio for a landing track when the track jump is conducted and increasesaid crosstalk elimination ratio while approaching said target track.20. The apparatus as claimed in claim 16, wherein said elimination ratioobtaining part maintains said crosstalk elimination ratio at “1” aftersaid crosstalk elimination ratio reaches “1”.
 21. The apparatus asclaimed in claim 2, further comprising a target reproduction signalstoring part storing said reproduction signal read from a target trackto be reproduced, wherein: said storing part includes two memories andstores a previous detected data detected from a previous track of saidtarget track and a next detected data detected from a next track of saidtarget track; said crosstalk signal generating part generates a previouscrosstalk signal and a next crosstalk signal based on said previousdetected data and said next detected data; and said crosstalk signaleliminating part deducts said previous crosstalk signal and said nextcrosstalk signal from said reproduction signal stored in said targetreproduction signal storing part.
 22. The apparatus as claimed in claim1, wherein when said recorded data is address information, saidcrosstalk signal generating part generates said crosstalk signal byconverting adjacent address information adjacent to said recorded datainto said waveform of said reproduction signal, so that saidreproduction signal showing said address information, in which saidcrosstalk signal is eliminated by said crosstalk signal eliminatingpart, is decoded in accordance with said predetermined algorithm toreproduce.
 23. The apparatus as claimed in claim 22, further comprisingan amplitude ratio calculating part calculating a ratio of a signalamplitude shift of said reproduction signal of a predetermined datapattern recorded in said address information, as said crosstalkelimination ratio, wherein said crosstalk signal eliminating partdeducts said crosstalk signal from said reproduction signal based onsaid crosstalk elimination ratio.
 24. The apparatus as claimed in claim22, further comprising a recording part recording said predetermineddata pattern shifting for a predetermined channel clocks when saidadjacent address information is recorded on said recording medium. 25.The apparatus as claimed in claim 23, further comprising: a map partmapping said crosstalk amount to said crosstalk elimination ratio; and acrosstalk amount obtaining part obtaining said crosstalk amountcorresponding to said crosstalk elimination ratio calculated by saidamplitude ratio calculating part from said map part, wherein saidcrosstalk signal eliminating part dedutes said crosstalk signal fromsaid reproduction signal based on said crosstalk amount.